Hot Cracking
Hot cracking occurs due to low-melting-point films on grain boundaries and thermal tensile stresses during cooling. It leads to a cracked structure and reduces the toughness of the steel.
Physical-Chemical Action Mechanism
Hot cracking occurs when the weld metal or the adjacent zone has low-melting-point films on grain boundaries during cooling. These low-melting-point films can form due to thermal tensile stresses during cooling. The stresses cause the metal to suddenly collapse and crack.
Metallurgical Relevance & Risks in Welding
Hot cracking can lead to severely cracked structures that significantly reduce the toughness of the steel. This can cause mechanical failure and shorten the service life of components. Additionally, it can lead to weld defects such as incomplete fusion or missing weld reinforcement.
Workshop Practice & Handling Instructions
To avoid hot cracking, it is important to cool the weld metal in a controlled and uniform manner. This can be achieved by using cooling water or cooling gas. The cooling rate should be set so that the metal cools slowly and continuously, without forming low-melting-point films on grain boundaries. A typical cooling time of 10-20 seconds per cm of steel thickness can help minimize the risk of hot cracks.